300 Tdi + LT77 Conversion
Mine is a 1986 into service Army 90 with an LT77 gearbox.
Let me just say that to carry this out you need to be handy with a welder and be prepared to improvise, but apart from that it works.
I did not fit the engine myself but I have done the additional modifications subsequently to introduce an intercooler and 300tdi air filter.
I know of one other person who managed to carry out the same conversion from my verbal explanation so it can't be that hard.
Also, I cannot take any credit for finding this out, it was a guy at a company called Motorshed in Chichester (01243 537684) that told me and did the job in the end (by the way £2500+VAT if you want him to do the job with 6000mile/6 month warranty).
ENGINE
The overall thing that stops most people is that the bell housing from an LT77 does not fit the 300 tdi engine.
Answer: source 300 tdi engine, remove 2.5 N/A engine from vehicle leaving g/box and bell housing in vehicle but support bell housing in roughly the right place.
On 2.5 N/A engine unbolt back plate and remove from the rear of the engine.
On 300 tdi engine remove rear back plate that includes the oil seal housing and oil seal, bolt 2.5 N/A back plate to rear of 300 tdi engine (it is a straight fit!).
300 tdi engine will now fit LT77 g/box!
In engine bay, remove old engine mounting brackets from chassis. They made up new engine mount brackets from angle steel.
Hang the engine in the engine bay and marry up to bell housing (might be best to leave the clutch off at this point).
Mark position for new engine mount brackets.
Remove engine and weld brackets to chassis.
The engine plus clutch should fit back in now and can probably be bolted in for good.
At this point you will notice that the engine sits along way back in the engine bay, on the 300 tdi vehicle the engine sits right up front with the fan by the radiator.
ANCILLARIES
This is where the tricky bit is, marrying up all the pipes and feeds.
The temp gauge wire needs lengthening and has a different terminal crimped on the end.
The throttle cable seems to fit from the original 2.5 N/A vehicle.
The fuel return pipe I think used to go via the fuel filter??? It looks like that hole has been plugged and now the fuel return goes directly to the tank (original fuel filter retained but you could source the 300 tdi one - I probably will eventually). The guy has used those quick release plumbing fittings to connect the semi-rigid fuel pipes.
IMPORTANT - OIL COOLER
The 300 tdi has two external oil pipes that connect to an oil cooler in the radiator. Two options here, (originally mine was like this) remove the pipes and blank off the exit holes the temp controlled valve on the output was removed and supplied with the engine for me to fit the pipes later.
Or source a 300 tdi radiator. I have now fitted a 300 tdi radiator, but the oil pipes weren't long enough you can source a custom set from a tractor place that does hydraulic hoses or buy a fancy stainless steel braided set from Goodridge or the likes.
EXHAUST
The fitter used most of my original 2.5 N/A exhaust. With your 300 tdi engine try and get a short length of exhaust with it.
The 300 tdi exhaust pipe leaves the turbo and when it straightens up it is cut off and the old exhaust conveniently is the right diameter to slide inside and is welded up.
I have now had a stainless steel one custom made of the right diameter full length and has made a huge difference (look for a fitter on www.powerflow.uk.com - ignore the fact that it is about boy racers). Remember the engine sits back further so a standard 300 tdi exhaust will not be a straight fit.
AIR FILTER
Originally the guy just used my 2.5 N/A air filter in the original housing in the original place. This is fine as no intercooler was fitted.
The exhaust gas recycling system is also removed - he suggested that they make the engine more unreliable when older and it also makes plumbing easier.
The Original 300 tdi air filter position is unsuitable as it bolts towards the rear of the engine and has a semi-rigid duct around the back of the engine to the turbo. As the engine now sits way back close to the bulkhead the duct won't fit.
To connect the turbo to the inlet manifold direct, source a selection of the 300 tdi turbo connecting pipes and go to a motor factors (I used Camberley Auto Factors) and they sell 2 or 3m straight lengths of steel pipe to make your own exhaust pipes. There is one exactly the right diameter for the inlet rubber connections (note the connection onto the 300 tdi inlet manifold is slightly larger than the rest).
The turbo to air filter connection is made up of a couple of flexible pipes that I think are used on the 300 tdi vehicle that connect the driver's wing mounted grille inlet to the inlet of the air filter on the engine. You can buy short pipe sections specially designed for joining pipe/ducting together (for rubber connecting pipes and these short connectors see www.eurospares.com - they have them and are a lot cheaper than buying land rover items). One end of the 2 flexible pipes joined together goes onto the turbo, the other fits inside the large rubber pipe from the air filter of the original filter that went onto the inlet manifold before.
He connected the engine breather pipe by using 2x300 tdi pipes linked together and connected to the original air filter breather inlet. I didn't like this as oil was sucked onto the air filter and clogged it after quite a while but this gets you going at first.
I have now sourced the correct intercooler and radiator assembly and fitted this but it means the original air filter housing masks the intercooler connections.
As you see later I removed the fan and now have fitted a 300 tdi air filter facing forward instead of backwards, on a flat plate using the 300tdi air filter clamps and rubber posts sited on the flat area above the fuel pump. I used a series of 300 tdi rigid ducts (the type that original only one connected the air filter to the turbo) to connect it to the 2 flexible ducts that are connected to the turbo.
Then I could connect up the intercooler using the correct rubber pipes and pieces of exhaust tube (as mentioned earlier), again suggest you buy the bits from Eurospares.
The engine breather pipe was removed from the original position and connected to the correct point on the semi-rigid duct from the 300 tdi, this way the oil particles go into the turbo instead of clogging the air filter.
RADIATOR
Connecting the radiator requires a bit of trickery. The guy used a combination of 2.5 N/A hoses and 300tdi ones as well linked together. He made up some lengthening pipes out of steel pipe to join one or two of them.
I have subsequently fitted the 300 tdi radiator and just bought a new set of pipes and lengthened then using the steel pipes he had made.
You can buy plastic right angle pipe connections etc from motor factors and the fitter used a couple of these to marry the 300 tdi water pipes to the heater matrix pipes.
AIR FLOW
In my set up the fan sat in mid air well away from the radiator cowling and under engine braking used to just touch the steering box (RHD) such that you heard a slight rattle, so I carefully shaved a little bit of plastic off each blade and it was fine.
I have now removed the viscous fan and coupling and source an electric fan from a scrap yard for £15 (off a rover 218 diesel) and wired that up with an override switch to turn it on in case of a problem with the automatic system (I am going to later wire in a cut out switch to prevent it operating when in water).
To automate the electric fan, I took the radiator to a radiator re-corer who fitted a boss to accept a radiator electric fan temp switch as fitted to other cars.
By the way the fan is switched by a relay as it has a huge in-rush current at start - mine had to have a 30A fuse but it runs using a lot less when up to speed. The engine runs very cool around town and barely gets over the 1/4 point on the gauge, on a motorway it gets up to the 1/2 way.
1. part of 300tdi rigid air duct as inlet to air filter hosing.
2. lengthened engine breather onto 300tdi rigid air duct.
3. 300tdi rigid air duct lengthened by short section cut from additional 300tdi rigid air duct.
4. steel exhaust pipe from turbo to intercooler: exit turbo - 2x right angle rubber hoses and rubber hoses one at intercooler and one mid length.
5. 2x flexible inlet hoses from rigid air duct onto turbo inlet.
1. original fuel filter.
2. original coolant tank.
3. electric fan from Rover 200 diesel.
4. 300tdi radiator and intercooler assembly.
5. lengthened coolant hose using steel pipe.
6. intercooler to inlet manifold by steel exhaust pipe and LR rubber hoses.
Air filter removed from original 300tdi mounting brackets
1. joint of 300tdi coolant hose to original coolant hose to expansion tank - not uses small metal inner pipe to allow jubilee clip to be used.
2. lengthened oil cooler pipes using UK plumbing compression joints.
3. steel mounting plat to accommodate 300tdi air filter mounting brackets - note the cut out (arrowed) for the inlet to the air filter.
1. LT77 bell housing
2. 2.5 N/A engine back plate.
3. 2.5 N/A clutch slave cylinder.
4. 300tdi engine sump (slightly cut down I think)
1. LT77.
2. bell housing.
3. original cross member
4. 300tdi RH bracket - note LH cut off as near to 2.5 N/A clutch slave cylinder.
5. front prop shaft
Steel angle bracket welded to chassis for RH engine mount - LH very similar.
I would like to thank Adrian for excellent the write up and pictures.